The proposed research involves the total synthesis of various spiro-, di-, and tricyclic sesquiterpenes using photochemical rearrangements of appropriately substituted cross-conjugated cyclohexadienones as key steps to obtain the ring skeleton of the natural products. Some of the target molecules have been shown to possess tumor inhibitory properties. Work is presently in progress on the total synthesis of plus or minus-euparotin, plus or minus-alpha-cadinol, plus or minus-T-murrolol, plus or minus-acorenone B, and plus or minus-mexicinin E. Several alkyl-substituted tricyclo (4.4.0.0. 2,6) decan-3-ones have been prepared by photochemical rearrangement of the corresponding cross-conjugated dienones followed by reduction. The mode of cleavage of the cyclopropane ring in these compounds with electrophilic reagents is being studied. These reactions appear to provide useful routes to various spiro- and bicyclic natural products. BIBLIOGRAPHIC REFERENCES: "The Synthesis of dl-Yomogin," D. Caine and G. Hasenhuettl, Tetrahedron Lett., 743 (1975); "Photochemical Rearrangements of Cross-Conjugated Cyclohexadienones. Application to the Synthesis of minus-4-Epiglobulol and plus-4-Epiaromadendrene," D. Caine and J. T. Gupton, III, J. Org. Chem., 40, 809 (1975).